Hydraulic transmission



R. TYLER HYDRAULIC TRANSMISS ION May 19, 1942.

Filed May 24, 1940 INVENTOR.

HAN-SUM TYLER BY I W Patented May 19, 1942 2,283,516 nrpnaoucTRANSMISSION Ransom Tyler, Greenfield, Win, assignor to The OilgearCompany, Milwaukee, Wis., a corporation of Wisconsin Application May 24,1940, Serial No. 336,909

6 Claims.

This invention relates to hydraulic transmissions of the type employedto transmit power intermittently. The transmission to which theinvention relates in particular includes a hydraulic motor, anaccumulator for supplying liquid to the motor at a rapid rate to causethe motor to operate at high speed and a pump for charging theaccumulator.

An object of the invention is to provide a transmission of thischaracter with means for bypassing both the pump and the motor when theaccumulator is nearly discharged. I

Another object is to provide a transmission having a reciprocating motorand means for bypassing the motor when it has completed its stroke.

Another object is to provide a transmission with an accumulator havingincorporated therein valve means for bypassing the motor when theaccumulator is nearly discharged.

Another object is to provide a transmission with an accumulator havingincorporated therein valve means for permitting liquid to escapetherefrom when the accumulator is fully charged and for bypassing themotor when the accumulator is nearly discharged.

Other objects and advantages will appear from the following descriptionof the transmission shown schematically in the accompanying drawing inwhich the views are as follows:

Fig. 1 is a diagram of the hydraulic circuit of a transmission in whichthe invention is embodied, the parts being shown in the positionsoccupied when the motor is idle and the accumulatonfully charged.

Fig. 2 is a view showing the accumulator fully discharged.

Fig. 3 is a view showing the control valve in a position differentfromthat shown in Fig. 1.

For the purpose of illustration, the invention has been shown embodiesin a transmission having a reciprocating motor of the spring return typebut it is to be understood that the invention may be as readily embodiedin a transmission having a difierent type of motor, such as a rotarymotor which is to operate intermittently or a reciprocating motor whichis operated in both directions by liquid.

As shown, the transmission includes a hydraulic motor I consisting of astationary cylinder 2, a piston 3 fitted in cylinder 2 and provided witha rod 4 which extends through one -end only of cylinder 2, and a spring5 for retracting piston 3.

Liquid for operating motor I is supplied thereto by a constant deliverypump 6 and an accumulator I under the control of a valve 6 having twoheads or pistons 9 and I0 formed thereon and closely fitted in the boreof a stationary valve casing ll, valve 6 being constantly urged downwardin respect to the drawing by a spring l2 arranged between piston l0 andthe end of casing Pump 6 draws liquid from a reservoir l5 and dischargesit into a supply channel, I6 which has a check valve I'I arrangedtherein to protect pump 6 from high pressures resulting from the suddenstalling or motor I.

Supply channel I6 is connected to control valve casing II at a pointbetween pistons 9 and I0, the upper end of motor cylinder 2 is connectedby a channel l8 to valve casing II at a point above piston l0, and bothends of valve casing II are connected to a drain channel I9 whichdischarges into reservoir l5.

Accumulator I includes a stationary cylinder 20 having a bore 2| formedtherein, a plunger 22 fitted in bore 2| and a spring 23 which constantlyurges plunger 22 upward and is arranged in a stationary spring chamber24.

Cylinder 20 is connected at its upper end to supply channel l6 and hastwo annular grooves or ports 25 and 26 formed in the wall of bore 2|.Port 25 has a branch of drain channel I9 connected thereto, port 26 isconnected by a channel 21 to channel l8 intermediate the ends thereof,and communication between ports 25 and 26 is controlled by plunger 22which has a reduced portion 28 formed in the lower part thereof so thatports 25 and 26 communicate with each other when plunger 22 is in itsupper position as shown in Fig. 2.

Operation If the parts are in the positions shown in Fig. 1 and pump 6is started, pump 6 will draw liquid from reservoir l5 and dischargeitinto channel l6. Since communication between channels IS and I8 isblocked by valve 8, pump pressure will rise until it reaches apredetermined maximum as determined by the resistance of accumulatorspring 23 and then the liquid discharged by ",spring 23 will moveplunger 22 upward at a very high speed and cause it to expel liquid frombore 2| into channel I6. This liquid, together with the liquiddischarged by pump 6 during upward movement of plunger 22, will flow ata very rapid rate through channel I6, valve casing II and channel I8 tothe upper end of motor prepare accumulator l-for the next cycle ofoperation.

The speed of piston 3 and the force exerted by it during or at the endof its working stroke will depend largely upon pump pressure and themasses to be moved, it being found in actual practice that a smallpiston operated from an accumulator system is capable of making acomplete reciprocation through a distance of nine inches in less thanone tenth of a second. The overall speed of motor I will depend upon thespeed at which valve 8 can be operated eiliciently and the volumetriccapacity of pump 6, one hundred or more strokes per minute beingordinarily required.

Means for operating valve 8 have not been shown for the reason that suchmeans form no part of the present invention. Ordinarily however, valve 8is operated through suitable linkage by a cam which moves it to theposition shown in Fig. 3 and then releases it to permit spring I2 toreturn it to the position shown in Fig. 1.

If motor I is to perform it work at a point intermediate the ends oftheworking stroke of piston 3, such as performing a punching or cuttingoperation, motor I and accumulator I are ordinarily so proportioned thatthe volume of liquid expelled from bore. 2| by piston 22 during itsupward movement is just sufficient to cause piston 3 to make a stroke ofthe desired length so that, when piston 3 reaches the end of its workingstroke, plunger 22 will have been raised high enough for the reducedportion 28 thereof to connect port 26 to port 25 (Fig. 2) and therebyreduce pump pressure substantially to zero. Spring 5 will then raisepiston 3 and cause it to eject liquid from the upper end of motorcylinder 2, through channels I8 and 21, ports 25 and 26 and drainchannel I9 into reservoir I5, and the liquid discharged by pump 6 atthis time will flow through channel I6, valve casing II, channels I6 and21 and ports 25 and 26 into drain channel I9. If valve 8 is released sothat spring I2 can return it to the position shown in Fig. 1 before orduring the return stroke of piston 3, all or a part of the liquidejected from cylinder 2 by piston 3 will flow through channel I8 andvalve casing II into drain channel I9.

If motor I is to perform its work at the end of the working stroke ofpiston 3, such as performing a riveting operation, the work piece is soarranged as to cause piston 3 to stall before Y plunger 22 rises highenough to open port 26 to v V port 25.. When piston 3 stalls, the liquiddischarged by pump 6 willventer bore 2| and move plunger 22 downward toprepare accumulator 'I for,-the next cycle of operation regardless ofwhether or not valve 8 has been returned to the position shown inFig. 1. Then when valve 8 .retumed to the position shown in Fig. 1,spring 5 will raise piston 3 as previously explained.

The high speed transmission disclosed herein by said pump with liquidfor operating said motor, said accumulator being provided with meanseffective during operation of said pump and responsive to saidaccumulator being nearly charged for connecting said channel means todrain.

2. In a hydraulic transmission, the combination of a motor, a pump forsupplying liquid to said motor, channel means including a valve forconnecting said motor either to said pump or to drain, an accumulatorconnected to said channel means between said valve and said pump andprovided with means for bypassing said pump in response to saidaccumulator becoming fully charged, and means operable with saidaccumulator for directing the discharge from said pump and saidaccumulator to drain in response to said accumulator becoming nearlydischarged.

3. In a hydraulic transmission, the combination of a motor, a pump forsupplying liquid to said motor, channel means including a valve forconnecting said motor either to said pump or to drain, an accumulatorcylinder having the pressure end thereof connected to said channel meansbetween said pump and said valve and having a port formed thereinintermediate the ends thereof and connected to drain and a second portspaced from said first port and connected to said channel means, springmeans arranged at the other end of said accumulator cylinder, and aplunger fitted in said accumulator cylinder in engagement with saidspring means so that liquid delivered to said accumulator cylinder bysaid pump will move said plunger against the resistance of said springmeans until the end of said plunger uncovers said first port and permitssaid pump to discharge therethrough to drain, said plunger having areduced portion so positioned that movement of said plunger apredetermined distance toward said pressure end will cause said portionto connect said ports to each other;

4. In a hydraulic transmission, the combination of a stationarycylinder, a piston fitted in said cylinder and constantly urged towardits retracted position, a pump for supplying liquid to said cylinder,channel means including a valve for connecting said cylinder either tosaid pump or to drain, and an accumulator connected at its pressure endto said channel means between said valve and said pump and adapted to becharged by said pump with liquid for operating said piston, saidaccumulator being provided with means efiective during operation of saidpump and reretracted position, a pump for supplying liquid to saidcylinder, channel means including a valve for connecting said cylindereither to saidpump or to drain, an accumulator connected to said channelmeans between said valve and said pump and provided with means forbypassing said pump in response to said accumulator becoming fullycharged, and means operable with said accumulator for directing thedischarge from said pump and said accumulator to drain in response tosaid accumulator becoming nearly discharged.

6. In a hydraulic transmission, the combination of a stationarycylinder, a piston fitted in said cylinder and constantly urged towardits retracted position, a pump for supplying liquid to said cylinder,channel means including a valve for connecting said cylinder either tosaid pump or to drain, an accumulator cylinder having the pressure endthereof connected to said channel means between said pump and said valveand having a port formed therein intermediate the ends thereof andconnected to drain and a second port spaced from said first port andconnected to said channel means, spring means arranged at the other endof said accumulator cylinder, and a plunger fitted in said accumulatorcylinder in engagement with said spring means so that liquid deliveredto said accumulator cylinder by said pump will move said plun er againstthe resistance of said spring means until the end oi. said plungeruncovers said first port and permits said pump to discharge therethroughto drain, said plunger having a reduced portion so positioned thatmovement of said plunger a predetermined distance toward said pressureend will cause said portion to connect said ports to each other.

RANSOM TYLER.

